linux-kernel - Re: [PATCH] block: Check ADMIN before NICE for IOPRIO_CLASS

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Message-ID: <74179f08-3529-7502-db33-2ea18cab3f58@kernel.dk>
Date:   Mon, 15 Nov 2021 11:04:55 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Alistair Delva <adelva@...gle.com>, linux-kernel@...r.kernel.org
Cc:     Khazhismel Kumykov <khazhy@...gle.com>,
        Bart Van Assche <bvanassche@....org>,
        Serge Hallyn <serge@...lyn.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Paul Moore <paul@...l-moore.com>, selinux@...r.kernel.org,
        linux-security-module@...r.kernel.org, kernel-team@...roid.com,
        stable@...r.kernel.org
Subject: Re: [PATCH] block: Check ADMIN before NICE for IOPRIO_CLASS_RT

On 11/15/21 10:38 AM, Alistair Delva wrote:
> Booting to Android userspace on 5.14 or newer triggers the following
> SELinux denial:
> 
> avc: denied { sys_nice } for comm="init" capability=23
>      scontext=u:r:init:s0 tcontext=u:r:init:s0 tclass=capability
>      permissive=0
> 
> Init is PID 0 running as root, so it already has CAP_SYS_ADMIN. For
> better compatibility with older SEPolicy, check ADMIN before NICE.

Seems a bit wonky to me, but the end result is the same. In any case,
this warrants a comment above it detailing why the ordering is
seemingly important.

-- 
Jens Axboe